SOME PROMISING WALNUT SELECTIONS (Juglans regia L.)

Evaluation of the economic characteristics of the fruit of 45 superior Camellia weiningensis Y.K. Li. trees

Reports related to Camellia weiningensis Y.K. Li. are rare. We evaluated the economic characteristics of the mature fruit of 45 superior C. weiningensis trees using principal component analysis (PCA) and gray correlation analysis, and identified excellent germplasms according to performance. PCA was employed to reduce the dimensions. PCA was performed for the original 15 indices of fruit diameter, fruit length, fruit shape, single-fruit weight, pericarp thickness, oil yield, fresh seed rate, dry seed rate, dry kernel rate and palmitic acid, stearic acid, linolenic acid, oleic acid, linoleic acid and arachidonic acid contents. According to the requirements of a cumulative contribution rate ≥ 80% and an eigenvector value > 1, six principle components were selected. These indices underwent weighted summation to establish a function model for comprehensive evaluation. Finally, the comprehensive rankings of the cultivars according to PCA were compared with those according to gray correlation analysis. The genetic variation coefficients of the 15 parameters ranged from 2.24% (oleic acid content) to 22.70% (single-fruit weight, with a range of 21.34 g). The top ten excellent cultivars with the highest comprehensive scores according to PCA and those according to gray correlation analysis were compared. According to PCA, oleic acid content, fruit diameter, fruit length, pericarp thickness, arachidonic acid content and dry seed rate can serve as representative evaluation indicators of C. weiningensis. The outcomes obtained based on PCA were basically consistent with those obtained based on gray correlation analysis. Finally, nine excellent cultivars were finally determined, i.e., WY-1, WY-6, WY-8, WY-25, WY-27, WY-30, WY-33, WY-35, WY-38 and WY-44. The results obtained in terms of crown yield were basically consistent with the outcomes of the comprehensive assessments, which indicates the reliability of the assessment methods used in this study.

Genetic diversity of superior Persian walnut genotypes in Azadshahr, Iran

Persian walnut (Juglans regia L.) is known to have originated in central and eastern Asia. Remnants of these wild populations can still be found in the Hyrcanian forest in north-eastern Iran. In this study, 102 individual walnut trees from four geographic populations in the Azadshahr province (Vamenan, Kashidar, Rudbar and Saidabad) were sampled. We characterized individual trees using 28 standard morphological traits. The range of traits varied widely for some economically important characteristics including nut weight (6.1-19.79 g), kernel weight (2.9-9.4 g), and kernel fill percentage (26.51-60.34%). After morphological evaluation, 39 superior individuals based on nut quality and kernel fill percentage were selected for further genetic analysis. Individual superior trees were genotyped using 10 simple sequence repeat markers (SSR) and genetic diversity. Number of alleles per locus ranged from 3 (WGA005) to 12 (WGA054). Clustering analysis of 10 SSR loci divided the genotypes into three main groups. PCoA analysis clearly sorted genotypes into one of four distinctive groups which aligned with the cluster analysis. All analyses showed that individuals from Saidabad were genetically distinct. Likewise, results indicated that the high level of genetic diversity in Azadshahr region walnuts may provide a diverse source for superior walnuts in walnut breeding programs.

Walnut (Juglans regia L.): genetic resources, chemistry, by-products

Walnut (Juglans regia L.) is the most widespread tree nut in the world. There is a great diversity of genotypes differing in forestry, productivity, physical and chemical nut traits. Some of them have been evaluated as promising and may serve as germplasm sources for breeding. The nutritional importance of the nut is related to the seed (kernel). It is a nutrient-dense food mainly owing to its oil content (up to 740 g kg(-1) in some commercial varieties), which can be extracted easily by screw pressing and consumed without refining. Walnut oil composition is dominated largely by unsaturated fatty acids (mainly linoleic together with lesser amounts of oleic and linolenic acids). Minor components of walnut oil include tocopherols, phospholipids, sphingolipids, sterols, hydrocarbons and volatile compounds. Phenolic compounds, present at high levels in the seed coat but poorly extracted with the oil, have been extensively characterised and found to possess strong antioxidant properties. The oil extraction residue is rich in proteins (unusually high in arginine, glutamic and aspartic acids) and has been employed in the formulation of various functional food products. This review describes current scientific knowledge concerning walnut genetic resources and composition as well as by-product obtainment and characteristics.